/**
 * Copied from https://gist.github.com/EmilHernvall/953733
 */
package com.sitewhere.rest.client;

import java.io.ByteArrayOutputStream;

public class Base64 {
    public static String encode(byte[] data) {
	char[] tbl = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S',
		'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
		'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8',
		'9', '+', '/' };

	StringBuilder buffer = new StringBuilder();
	int pad = 0;
	for (int i = 0; i < data.length; i += 3) {

	    int b = ((data[i] & 0xFF) << 16) & 0xFFFFFF;
	    if (i + 1 < data.length) {
		b |= (data[i + 1] & 0xFF) << 8;
	    } else {
		pad++;
	    }
	    if (i + 2 < data.length) {
		b |= (data[i + 2] & 0xFF);
	    } else {
		pad++;
	    }

	    for (int j = 0; j < 4 - pad; j++) {
		int c = (b & 0xFC0000) >> 18;
		buffer.append(tbl[c]);
		b <<= 6;
	    }
	}
	for (int j = 0; j < pad; j++) {
	    buffer.append("=");
	}

	return buffer.toString();
    }

    public static byte[] decode(String data) {
	int[] tbl = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53,
		54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
		13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32,
		33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 };
	byte[] bytes = data.getBytes();
	ByteArrayOutputStream buffer = new ByteArrayOutputStream();
	for (int i = 0; i < bytes.length;) {
	    int b = 0;
	    if (tbl[bytes[i]] != -1) {
		b = (tbl[bytes[i]] & 0xFF) << 18;
	    }
	    // skip unknown characters
	    else {
		i++;
		continue;
	    }

	    int num = 0;
	    if (i + 1 < bytes.length && tbl[bytes[i + 1]] != -1) {
		b = b | ((tbl[bytes[i + 1]] & 0xFF) << 12);
		num++;
	    }
	    if (i + 2 < bytes.length && tbl[bytes[i + 2]] != -1) {
		b = b | ((tbl[bytes[i + 2]] & 0xFF) << 6);
		num++;
	    }
	    if (i + 3 < bytes.length && tbl[bytes[i + 3]] != -1) {
		b = b | (tbl[bytes[i + 3]] & 0xFF);
		num++;
	    }

	    while (num > 0) {
		int c = (b & 0xFF0000) >> 16;
		buffer.write((char) c);
		b <<= 8;
		num--;
	    }
	    i += 4;
	}
	return buffer.toByteArray();
    }
}